Material not displaying on array objects
In texture the coordinates node, you have it set to object, the scale then refers to the original object and doesn't get passed on to the ones created by the modifiers. Effectively you now have a bigger object and the texture doesn't cover all of it, and also the center of the object is now in a different place.
If you UV unwrap the original plane, then the texture will follow on the object created by modifiers.


To get an accurate image of what your textures look like switch to "rendered" view on the viewport.